In a typical electric power steering (EPS) system of a vehicle, a hand wheel torque sensor is used to determine the driver requested assist torque. When the hand wheel torque sensor becomes faulty and does not function properly, the EPS system may not be able to provide the assist torque. In some cases, the vehicle is also put in a Limp Home mode, in which the vehicle operates in a limited fashion, when the hand wheel torque sensor becomes degraded. Accordingly, it is desirable to have an EPS system that better handles a situation of a degraded hand wheel torque sensor.
In an electric power steering (EPS) system, the assist torque provided by a motor typically reduces the steering effort by a driver. In certain situations, such as when a torque sensor that is used to determine the driver requested assist torque degrades, the assist torque is instantly switched off. When the EPS system stops providing the assist torque, there is a possibility of a sudden perceptible change that the driver may feel on the hand wheel torque. This is because an instantaneous removal of the assist torque allows the stored energy in the system to back-drive the motor with some velocity. It is therefore desirable to provide an EPS system that handles this stored energy and eliminate the sudden perceptible change on the hand wheel.